Effects of Post Heat-Treatment on Surface Characteristics and Adhesive Bonding Performance of Medium Density Fiberboard

Nadir Ayrilmis1 and Jerrold E. Winandy2

1Department of Wood Mechanics and Technology, Forestry Faculty, Istanbul University, Istanbul, Turkey 2USDA Forest Service, Forest Products Laboratory, Madison, Wisconsin, USA

A series of commercially manufactured medium density fiberboard (MDF) panels were exposed to a post-manufacture heat-treatment at various temperatures and durations using a hot press and just enough pressure to ensure firm contact between the panel and the press platens. Post- manufacture heat-treatment improved surface roughness of the exterior MDF panels. Panels treated at 225� C for 30 min had the smoothest surface while the roughest surface was found for the control panels. Wettability and the adhesive bonding strength between veneer sheet and panel surface were decreased as post-treatment press temperature increased. A significant relationship (R2 = 092) existed between contact angles and adhesive bond strength.

Keywords Bonding strength; Contact angle; Delamination; Heat treatment; Mechanical properties; Medium density ﬁberboard; Physical properties; Post heat-treatment; Surface characteristics; Surface roughness; Surface wettability; Thermal modiﬁcation; Thermal treatment; Wood; Wood composite.

1. Introduction adhesion problems because of the interference with wetting, Medium density fiberboard (MDF) is one of the most flow, and penetration of adhesive, and also interfere with rapidly growing composite panel product in the market. the cure and resulting cohesive strength of the adhesive. Sernek et al. [5] reported that wood drying at temperatures Smooth and solid edges of MDF can be easily machined � and finished, and the uniform surface provides an excellent between 160 and 180 C caused modifications in surface substrate for painting or applying decorative overlays. composition. However, the disadvantage of MDF compared to plywood Wettability is crucial for good adhesion in wood bonding. is that when MDF has contact with water, it generally The adhesive has to wet, flow, and penetrate the cellular swells more than plywood, and a higher proportion of structure of wood in order to establish intimate contact that swelling may not be recoverable after drying. The between molecules of wood and adhesive [6]. There is in-plane movements arised from increased or decreased evidence about the positive relationship between wood moisture content of the panel can cause high internal stresses wettability and adhesion [7]. Many experiments have shown due to the restraint offered by fastening such as nails in that high drying temperature reduces the wood adhesive construction. These stresses may be large enough to cause bonding strength, or that high temperature decreases wood buckled panels, pushed-out nails, and separation of the panel hygroscopicity and hinders wettability [3, 8–10]. Wood from the structure. Swelling and expansion properties, thus, fibers become hydrophobic after heat treatment, and their is one of the most important properties of the fiberboards. wetting capability becomes less after heat treatment [3]. Heat treatment improves the hygroscopic characteristics The wettability of wood can be characterized by contact of wood, but it can also change its surface characteristics angle analysis. This analysis is important to determine the and, therefore, their wetting properties [1]. A wood surface, adhesive and coating properties of wood and wood-based which is exposed to high temperature condition, can composite surfaces [2]. When contact angle is zero, perfect experience surface inactivation [2, 3]. Several known wetting of a surface occurs. Contact angle is a useful index changes, especially oxidation, occur to the wood surface of adhesive effectiveness. over time during exposure to high temperature. Inactivation MDF panels are used to manufacture molding, laminated of wood surfaces, which results in poor bond quality, flooring, overlaid panels for furniture and cabinet industry. is a time-dependent process accelerated by increasing When the panels are used as substrate for thin overlays temperature [4]. An inactivated wood surface can cause their surface characteristics in terms of roughness play an important role in determining quality of final product. There are various methods to evaluate surface roughness Received August 14, 2008; Accepted October 10, 2008 of composite panels, which include acoustic emission, Address correspondence to Nadir Ayrilmis, Department of Wood pneumatic, laser, and stylus [11]. The stylus technique is Mechanics and Technology, Forestry Faculty, Istanbul University, extensively used and well established to quantify surface Bahcekoy, Sariyer, Istanbul 34473, Turkey; Fax: +90-212-226-1113; roughness of industrial metal and plastic parts. The main E-mail: [email protected] advantage of the stylus method is having standard numerical 594 SURFACE PROPERTIES OF HEAT-TREATED FIBERBOARD 595

parameters and profile of the surface. Previous studies used for surface roughness evaluations. A total of six reported that surface roughness values of heat-treated wood measurements with a 15-mm tracing length, 3 parallel to and veneer sheets decreased with increasing treatment the sand marks and 3 perpendicular to the sand marks, temperature and treatment times [12–14]. were taken from each face of the samples. Prior to the test, From the literature, we knew that post-manufacture each sample was conditioned in a climate chamber with a heat-treatment decreased swelling, enhanced resistance of temperature of 20�C and a relative humidity of 65% until the wood-based panels to moisture absorption, and enhanced they reached to the equilibrium moisture content (12%). The durability and fungal resistance of materials [15–18]. It has points of roughness measurements were randomly marked also been observed that heat-treatment of solid wood at high on the surface of test samples. A Mitutoyo SJ-301 surface temperatures causes changes in the surface characteristics roughness tester, stylus type profilometer, was employed for and adhesive bonding performance of wood [8, 9]. But the surface roughness tests. it has not been widely studied whether similar changes Three roughness parameters characterized by ISO 4287 in dry process fiberboard (MDF). An extensive literature [19] standard, respectively, average roughness Ra, mean search did not reveal any information about the effects of peak-to-valley height Rz, and maximum peak-to-valley post heat-treatment on surface characteristics and adhesive height Ry were considered to evaluate the surface bonding performance of exterior MDF. The objective of this characteristics of the panels. The average roughness is by research was to investigate the effects of post-manufacture far the most commonly used parameter in surface finish heat-treatment on the surface characteristics and adhesive measurement. Ra is the arithmetic mean of the absolute bonding strength of the heat-treated MDF panels. values of the profile deviations from the mean line. Typical roughness profiles of the samples are shown in Fig. 1. The 2. Materials and methods profilometer used for the measurements consisted of main unit and a pick-up which has a skid-type diamond stylus 2.1. MDF Panels � with 5 m tip radius and 90 tip angle. The stylus traversed Commercially manufactured MDF panels (16-mm thick) the surface at a constant speed of 10 mm/min, and measuring for the exterior siding and trim market were used in the force of the scanning arm on the samples was 4 mN (0.4 gf). experiments. These MDF panels had been bonded with a phenol-formaldehyde (PF) resin and shipped without the 2.4. Determination of Wettability of MDF Panels coatings or primers typically applied for typical exterior applications. We choose panels bonded with PF resin The wetting behavior of the heat-treated MDF surfaces because PF resin is a more heat-resistant, exterior-type resin. without veneer sheets was characterized by the contact Thirty 12m × 24 m commercial MDF panels were then angle method. The measurements were conducted with cut into smaller test panels 100 cm × 100 cm. The sixty the contact-angle instrument of Kruss GmbH (Easy Drop 100 cm × 100 cm test panels were then randomly assigned DSA-2) using distilled water drop at room temperature. to four experimental groups (an control and three levels of Determination of contact angle was performed using the heat-treatment). conic section method. An imaging system was used to measure contact angle and shape and size of water droplets for the tested surfaces of the MDF samples. The image 2.2. Post-Manufacture Heat-Treatment of the liquid drop was captured by a video camera and The MDF panels were loaded into a heated press the contact angle was measured by digital image analysis using a computer controlled single-opening hot press software. Contact angle from the images was measured at � and were thermally treated at either 175 C for 15 min, 5 s after the 5 L droplet of distilled water was placed on the � � 200 C for 30 min, or 225 C for 30 min. This press sample surface. Eight 50 mm × 50 mm samples from each system includes specially designed temperature-pressure of the four treatment groups were used for contact angle probes for measuring internal panel temperature and gas measurements of the MDF surfaces without veneers sheets. pressure during heat-treatment. A platen contact pressure Sixteen measurements (two from each of eight samples: of 150 (kPa) was applied to provide light but uniform one measurement for top surface and one measurement for contact between press plates and the panels’ surfaces. After bottom surface) were taken. Following to the contact angle heat treatment, all panels were cooled prior to stacking measurements, the droplets (5 L) on the MDF surfaces to further minimize fire hazards. 50 mm × 50 mm samples were wiped off using an absorbent tissue paper. The samples for the surface characteristic properties were cut from each were then reconditioned in a chamber with a temperature of 1m × 1 m MDF panel. In this study, we used these 50 mm × 20�C and a relative humidity of 65% until they reached to 50 mm samples to evaluate surface roughness, wettability, the equilibrium moisture content before the next evaluation and wood veneer-to-MDF adhesive bond strength. The of adhesive bonding strength. average density values of heat-treated and control panels varied from 0.79 to 081 g/cm3. The treated samples at all 2.5. Overlaying of MDF with Veneer Sheet temperature levels showed no differences in density when The top and bottom surfaces of the equilibrated MDF compared to control samples. samples were then overlaid with 0.65 mm thick sliced beech (Fagus orientalis Lipsky) veneer having dimensions of 2.3. Determination of Surface Roughness of MDF Panels 50 mm × 50 mm. Urea-formaldehyde (UF) resin was spread The eight 50 mm by 50-mm MDF samples (without on the surface of the MDF samples at the rate of 180 g/m2 veneer) from each of the four levels of treatment were using a roller prior to curing using a Carver bench-top press 596 N. AYRILMIS AND J. E. WINANDY

Figure 1.—Typical surface roughness profiles of control panel (A) and panel treated at 225�C for 30 min (B). at a temperature of 130�C and a pressure of 65 bar for 4 min. from the initial application of the force until failure of the Eight replicate overlaid samples were made from each of test sample was not less than 30 s and not more than 120 s. the four treatment groups before adhesive bonding strength One measurement from each of the eight replicate samples was evaluated using the delamination test. from each treatment group were evaluated for adhesive bond strength. 2.6. Delamination Strength between MDF Surface and Wood Veneer Sheet 2.7. Statistical Analysis Adhesive bonding strength between MDF surface and For surface roughness, wettability, and delamination veneer sheet (delamination test) was evaluated on veneer tests, all multiple comparisons were first subjected to an faced MDF samples according to DIN 68765 B1 [20]. On analysis of variance (ANOVA) at pr < 001 and significant the surface of the samples, a circle with a 35.7 mm diameter differences between mean values of the control and treated MDF test samples were determined using Duncan’s multiple was drilled through the veneer thickness. This veneer circle range test. on the MDF surface was separated from the surrounding veneer. A metal tension seal (pull-up seal) was glued with 3. Result and discussion polyurethane adhesive and placed in the movable crosshead of the universal test machine to remove the veneer circle 3.1. Surface Roughness Parameters from the MDF panel surface. The force was applied at an The Ra, Ry, and Rz values of variously heat-treated MDF even rate and the rate of application was adjusted so the time samples at each exposure condition are shown in Table 1.

Table 1.—Variations in average surface roughness, contact angle, and adhesive bonding strength values of the MDF samples as a result of thermal treatment.

Wettability Adhesive Heat-treatment Panel Surface roughness parameters (Contact bonding Panel level density Ra Ry Rz angle method) strength type (temperature/time) g/cm3 (m) degree (�) (N/mm2

A Control 0.81 5.38 A1 53.26 A 40.71 A 95.22 A 2.30 A (0.02) (0.55) (9.16) (5.21) (2.67) (0.05) B 175�C/15 min 0.78 4.84 B 46.62 B 35.26 B 114.19 B 2.17 B (0.01) (0.67) (5.76) (3.76) (3.63) (0.18) C 200�C/30 min 0.80 4.11 C 43.34 C 32.19 C 122.33 C 1.98 C (0.02) (0.29) (5.09) (2.95) (3.82) (0.08) D 225�C/30 min 0.79 3.82 C 41.57 C 30.32 C 130.32 D 1.85 D (0.02) (0.35) (4.22) (4.10) (4.09) (0.11)

1Groups with same letters in column indicate that there is no statistical difference (pr < 001) between the samples according to the Duncan’s multiply range test. Values in parentheses are standard deviations. SURFACE PROPERTIES OF HEAT-TREATED FIBERBOARD 597

In general, smoothness of the panels was improved as heat- of the heat-treated MDF panels decreased after heat treatment temparature increased. The Ra values surface exposure. In a previous study, wettability decrease was due roughness values of all treated MDF panels were lower than to the degredation of the most hygroscopic compounds, control MDF panels. Panels treated at 225�C for 30 min had hemicelluloses, and amorphous cellulose, but also to the smoothest surface with an Ra value of 382 m while the dehydratation reactions during heat treatment was reported roughest surface was found for the control panels having an [24]. Plastification of lignin starts affecting particularly the Ra value of 538 m (Fig. 1). The average surface roughness hydrophilic properties of the wood [3]. Peculiar behavior of value of panels treated at 225�C for 30 min was 29% lower wettability in relation to heat treatment for the test panels than control samples, followed by panels treated at 200�C may be explained at the cellular level. Hemicelluloses for 30 min (23% lower) and 175�C for 15 min (10% lower). are hydrolyzed during heat treatment, and this decreases This was in agreement with the results of previous studies the hygroscopity of heat-treated wood [25]. Exposure in solid wood and veneer sheets [12–14, 21]. The Ry and duration and temperature are two important factors affecting Rz values of the panels also decreased with increasing heat- hemicelluloses degradation. Cumulative heat exposure in treatment temperature. When compared to control MDF, all the hot-press alters the hemicellulose structure because surface roughness parameters (Ra, Ry, and Rz values) for the arabinan and galactan, each a side-chain component of the panels were significantly improved by heat-treatment, but hemicellulose, tend to be more degraded as both temperature no significant differences were noted between groups heat- and press duration increase. At very high temperatures, treated at temperatures ≥200�C (Table 1). This can clearly the hemicelluloses may be changed to furfural polymers, be observed by inspection of raw data from the surface which are less hygroscopic. In addition, at high temperatures roughness profilometer that recorded noticeably shallower moisture content strongly catalyzes the depolymerization ridges and valleys when compared to control panels as it processes of wood constituents. traversed the MDF surface at a constant speed. Heat-treated wood also exhibits lower affinity to water During heat-treatment, physical and chemical processes and a strongly modified wettability leading to important occur in layers near the surface that result in a modified changes of its behavior with most coating or gluing surface with new characteristics. After the glass transition processes [2]. A wood surface, which is exposed to a temperature (160�C) is achieved, plastification of lignin high-temperature condition, can experience inactivation. start to affect the surface characteristics of wood [22]. The Oxidation and/or pyrolysis of wood surface bonding heat treatment apparently resulted in such a plastification sites are real and inevitable inactivation mechanisms at on the MDF surfaces. High temperatures above 160�C high enough temperatures and long times. A loss of probably caused lignin to reach a thermoplastic condition hygroscopicity is assigned to a gradual loss of wood and thus densify panel surface. Better surface quality of hydroxyl groups during drying. This is one of the the heat-treated MDF can also be related to this additional mechanisms responsible for poor adhesion of the thermally surface densification on the face of the MDF panel. The inactivated wood. The rate of degradation is much faster at surface-densified MDF samples exhibited a glossy and extremely high processing temperature. In a previous study, smooth appearance after heat treatment. Moisture in the it was reported that overdrying inactivated the surfaces manufactured MDF panel is transformed to steam when of Douglas-fir veneer, resulting in poor wettability [26]. hot press platens contact to the panel surfaces. This steam Similar results showing negative effect of heat treatment on tends to soften the fibers near the surface layers also plays wood wettability were also found by many authors [2, 3, a part in MDF surface compaction and plasticization which 9, 24]. Wettability is directly related to the oxygen:carbon improves the surface smoothness. (O/C) ratio and inversely related to the C1/C2 ratio [23]. The C1 component is related to carbon–carbon or 3.2. Wettability carbon–hydrogen bonds, and the C2 component represents The contact angle values of the heat-treated MDF samples single carbon–oxygen bonds. A low O/C ratio and a high are presented in Table 1. Significant differences (pr < 001) C1/C2 ratio reflects a high concentration of nonpolar wood between all groups were found to exist as determined by components (extractives/volatile compounds) on the wood Duncan’s multiple-comparison tests (Table 1). The contact surface, which modifies the wood surface from hydrophilic angle values for all treated panels increased after the heat to more hydrophobic. treatment. The contact angle measurements showed that post heat-treatment had a significant influence on the surface 3.3. Adhesive Bonding Strength between MDF Surface wettability of the treated MDF samples. The average contact and Veneer Sheet angle value of panels treated at 175�C for 15 min was 20% Adhesive bonding strength of the heat-treated MDF higher than control controls, followed by panels treated panels decreased with increasing contact angle value. at 200�C for 30 min (28% higher), and 225�C for 30 min Significant differences between treatment groups were (37% higher). determined individually by Duncan’s multiple-comparison The increase in contact angle may be interpreted as a tests (Table 1). All treatment groups were significantly decrease in hydrophilicity [23]. The surface of heat-treated different from each other and control group. The test values wood is less polar and thus repels water, resulting in of all treated panels were between 6 to 20% lower than the a lower wettability than in the case of untreated wood. average of the control control panels. The highest adhesive The hydrophilic character of wood is strongly affected by bonding strength was of 230 N/mm2 for the control, and the heat-treatment [1]. The sorption and diffusion properties lowest was of 185 N/mm2 for the panels treated 225�C for 598 N. AYRILMIS AND J. E. WINANDY

strength of exterior MDF panels. Heat-induced chemical modification resulted in surface inactivation of fibers in layers near the surface. 2. Increasing the severity of post-manufacture heat- treatment resulted in smoother surfaces. 3. The adhesive bonding performance decreased with the increasing contact angle. The bonding strength between veneer and panel surface was adversely affected by the post-manufacture heat-treatment. A significant relationship (R2 = 092) was found to exist between the adhesive bonding strength and the contact angle values. This relationship indicates that contact angle could be an indicator for the degree of adhesive bond strength of MDF. Figure 2.—Linear relationship between adhesive bonding strength 4. We suggest that MDF manufactures use modified glues, (delamination of the UF resin bondline between MDF-panel surface and a paints, or varnishes adapted to these inactivated MDF sheet of beech veneer) and contact angle values. surfaces to prevent in-service adhesion problems.

Acknowledgments 30 min. A linear relationship (R2 = 092) between contact angle and adhesive bonding strength values (delamination This work was supported by Research Fund of the strength) was found (Fig. 2). It is evident that the bonding Istanbul University. Project number: UDP-2455. The strength of the heat-treated panels was decreased with authors wish to acknowledge Research Fund of the Istanbul increasing contact angle. This result was consistent with University for financial support. previous studies [26, 27]. For MDF, this data shows that both changes in the contact angle values and in the rate of References change in the contact angle values were a clear indication of how strongly adhesion would develop between surfaces. 1. Garcia, R.A. Improvement of dimensional stability of medium The results obtained from our study indicated that density fibreboard by physical-chemical treatments. Ph.D. Thesis, the hydrophobic character of the heat-treated MDF Laval University: Quebec, Canada, 2005. could diminish the ability of waterborne thermoset 2. Petrissans, M.; Gerardin, P.; Elbakali, D.; Serraj, M. Wettability adhesives (aminoplasts) such as urea-formaldehyde and of heat-treated wood. Holzforschung 2003, 57, 301–307. melamine/urea formaldehyde to adequately wet the surface 3. Hakkou, M.; Petrissans, M.; Zoulalian, A.; Gerardin, P. and establish physical adhesion. As the UF resin used to Investigation of wood wettability changes during heat treatment adhere the veneer to the MDF was a polar adhesive, it on the basis of chemical analysis. Polymer Degradation and needed to wet the fibers to acheive adequate bonding and Stability 2005, 89, 1–5. to then develop bonds. However, its wetting capability was 4. Aydin, I. Activation of wood surfaces for glue bonds by influenced by a loss in the wettability of the fiber resulting mechanical pre-treatment and its effects on some properties of from heat treatment. This is why binding the cell polymers veneer surfaces and plywood panels. Applied Surface Science after heat treatment, which are chemically modified 2004, 233, 268–274. compounds, became problematic. Micropore closure affects 5. Sernek, M.; Kamke, F.A.; Glasser, W.G. Comparative analysis also adhesive penetration and wetting of the wood cell of inactivated wood surfaces. Holzforschung 2004, 58, walls. The closure of larger micropores limits penetration by 22–31. larger resin molecules, and thus, the bond strength and wood 6. Wood Handbook. Wood as an Engineering Material; United failure decreases [28]. This applies particularly in those States Department of Agriculture Forest Service, Forest Products cases where mechanical interlocking plays an important part Laboratory, USDA, Forest Service: Madison, WI, 1999. of the adhesion. The adhesion between the inactivated wood 7. Wellons, J.D. Adhesion to wood substrates. In ACS Symposium and MDF panel surfaces may be improved by several means. Series; Gould, R. F., Ed.; American Chemical Society: Treatment with chemicals, such as sodium hydroxide, Washington, DC, 1977; 150–168. calcium hydroxide, nitric acid, and, hydrogen peroxide 8. Christiansen, A.W. How overdrying wood reduces its bonding to [8] can partially improve adhesion. Surface cleaning and phenol formaldehyde adhesives: a critical review of the literature. surface removal, for example, by sanding also improve the Part I. Physical responses. Wood and Fiber Science 1990, 22, adhesion between inactivated surfaces. 441–459. 9. Podgorski, L.; Chevet, B.; Onic, L.; Merlin, A. Modification of 4. Conclusions wood wettability by plasma and corona treatments. International The following conclusions have been drawn from the Journal of Adhesion and Adhesive 2000, 20, 103–111. results of present work: 10. Follrich, J.; Muller, U.; Gindl, W. Effects of thermal modification on the adhesion between spruce wood (Picea abies Karst.) and a 1. Post-manufacture heat-treatment was a significant factor thermoplastic polymer. Holz Als Roh-Und Werkstoff 2006, 64, influencing of surface roughness, wettability, and bond 373–376. SURFACE PROPERTIES OF HEAT-TREATED FIBERBOARD 599

11. Ostman, B.A.L. Surface roughness of wood-based panels after 20. Deutsches Institut fur Normung. DIN 68765 B1: Spanplatten; aging. Forest Products Journal 1983, 33 (7/8), 35–42. Kunststoffbeschichtete dekorative Flachpreßplatten; Begriff: 12. Unsal, O.; Ayrilmis, N. Variations in compression strength Anforderungen, Germany, 1987. and surface roughness of heat-treated Turkish river red gum 21. Aydin, I.; Colakoglu, G. The effects of veneer drying (Eucalyptus camaldulensis) wood. Journal of Wood Science temperature on wettability, Surface roughness and some 2005, 51, 405–409. properties of plywood. 6th European Panel Products Symposium. 13. Korkut, D.S.; Guller, B. The effects of heat treatment on In Proceedings of the Sixth European Panel Products Symposium, physical properties and surface roughness of red-bud maple (Acer North Wales Conference Centre, Llandudno, October 9–11, North trautvetteri Medw.) wood. Bioresource Technology 2008, 99, Wales: UK, 2002; pp. 60–69. 2846–2851. 22. Follrich, J.; Muller, U.; Gindl, W. Effects of thermal modification 14. Gunduz, G.; Korkut, S.; Korkut, D.S. The effects of heat treatment on the adhesion between spruce wood (Picea abies Karst.) and a on physical and technological properties and surface roughness thermoplastic polymer. Holz Als Roh-Und Werkstoff 2006, 64, of Camiyani Black Pine (Pinus nigra Arn. subsp. pallasiana 373–376. var. pallasiana) wood. Bioresource Technology 2008, 99, 23. Sernek, M. Comparative analysis of inactivated wood surfaces, 2275–2280. Ph.D. Thesis, Virginia Polytechnic Institute and State University: 15. Hsu, W.E.; Schwald, W.; Shields, J.A. Chemical and physical USA, 2002. changes required for producing dimensionally stable wood-based 24. Esteves, B.M.; Domingos, I.J.; Pereira, H.M. Pine wood composites. Part 2: Heat post treatment. Wood Science and modification by heat treatment in air. BioResources 2007, 3, Technology 1989, 23 (3), 281–288. 142–154. 16. Kamdem, D.P.; Pizzi, A.; Jermannaud, A. Durability of heat- 25. Winandy, J.E.; Smith, W.R. Enhancing composite durability: treated wood. Holz Als Roh-Und Werkstoff 2002, 60, 1–6. using thermal treatments. In Proceed. Wood Protection. Michael 17. Okino, E.Y.A.; Teixeira, D.E.; Del Menezzi, C.H.S. Post-thermal Barnes, M., Ed.; March 21–23, Forest Products Society: treatment of oriented strandboard (OSB) made from cypress New Orleans, LA, USA, 2006; 195–199. (Cupressus glauca lam.). Maderas, Ciencia y Tecnologia 2007, 26. Poncsak, S.; Shi, S.Q.; Kocaefe, D.; Miller, G. Effect of thermal 9, 199–210. treatment of wood lumbers on their adhesive bond strength and 18. Del Menezzi, C.H.S.; Tomaselli, I. Contact thermal post durability. Journal of Adhesion Science and Technology 2007, treatment of oriented strandboard to improve dimensional 21, 745–754. stability: A preliminary study. Holz Als Roh-Und Werkstoff 27. Korkut, D.S.; Korkut, S.; Dilik, T. Effect of heat treatment 2006, 64, 212–217. on some mechanical properties of laminated window profiles 19. International Standard. ISO 4287. Geometrical product manufactured using two types of adhesives. International Journal specifications (GPS)—Surface texture: Profile method—Terms, of Molecular Science 2008, 9, 454–463. Definitions, and Surface Texture Parameters. International 28. Wellons, J.D. Wettability and gluability of Douglas-fir veneer. Organization for Standardization: Geneva, Switzerland, 1987. Forest Products Journal 1980, 30 (7), 53–55.